Ultrasonic instruments, including both hollow core and solid core instruments, are used for the safe and effective treatment of many medical conditions. Ultrasonic instruments, and particularly solid core ultrasonic instruments, are advantageous because they may be used to cut and/or coagulate tissue using energy in the form of mechanical vibrations transmitted to a surgical end effector at ultrasonic frequencies. Ultrasonic vibrations transmitted to organic tissue at suitable energy levels with a suitable end effector may be used to cut, dissect, elevate, or coagulate tissue or separate muscle tissue from bone cut. Solid core technology ultrasonic instruments are particularly advantageous because of the amount of ultrasonic energy that may be transmitted from the ultrasonic transducer to the surgical end effector through an ultrasonic transmission waveguide. Such instruments may be used for open procedures or minimally invasive procedures, such as endoscopic or laparoscopic procedures, wherein the end effector is passed through a trocar to reach the surgical site.
Activating or exciting the end effector of such instruments at ultrasonic frequencies induces longitudinal vibratory movement that generates localized heat within adjacent tissue, facilitating both cutting and coagulating. Because of the nature of ultrasonic instruments, a particular ultrasonically actuated end effector may be designed to perform numerous functions, including, for example, cutting, clamping, and coagulating.
Ultrasonic vibration is induced in the surgical end effector by electrically exciting a transducer, for example. The transducer may be constructed of one or more piezoelectric or magnetostrictive elements in the instrument hand piece. Vibrations generated by the transducer section are transmitted to the surgical end effector via an ultrasonic waveguide extending from the transducer section to the surgical end effector. The waveguides and end effectors are designed to resonate at the same frequency as the transducer. When an end effector is attached to a transducer the overall system frequency may be the same frequency as the transducer itself.
The transducer and the end effector may be designed to resonate at two different frequencies and when joined or coupled may resonate at a third frequency. The zero-to-peak amplitude of the longitudinal ultrasonic vibration at the tip, d, of the end effector behaves as a simple sinusoid at the resonant frequency as given by:d=A sin(ωt)where:ω=the radian frequency which equals 2π times the cyclic frequency, f; andA=the zero-to-peak amplitude.The longitudinal excursion is defined as the peak-to-peak (p-t-p) amplitude, which is just twice the amplitude of the sine wave or 2A.
Solid core ultrasonic surgical instruments may be divided into two types, single element end effector devices and multiple-element end effectors. Single element end effector devices include instruments such as scalpels (e.g., blades, sharp hook blades, dissecting hook blades, curved blades) and ball coagulators. Single-element end effector instruments have limited ability to apply blade-to-tissue pressure when the tissue is soft and loosely supported. Substantial pressure may be necessary to effectively couple ultrasonic energy to the tissue. The inability of a single-element end effector to grasp the tissue results in a further inability to fully coapt tissue surfaces while applying ultrasonic energy, leading to less-than-desired hemostasis and tissue joining. The use of multiple-element end effectors such as clamping coagulators includes a mechanism to press tissue against an ultrasonic blade that can overcome these deficiencies.
Ultrasonic clamp coagulators provide an improved ultrasonic surgical instrument for cutting/coagulating tissue, particularly loose and unsupported tissue, wherein the ultrasonic blade is employed in conjunction with a clamp for applying a compressive or biasing force to the tissue, to achieve faster coagulation and cutting of the tissue with less attenuation of the blade motion.
As the distal end of the end effector, or more particularly, the blade, cuts through or coagulates tissue it comes into contact with fluid. The fluid may comprise irrigation fluid, blood, tissue particles and/or any combination thereof. When the distal end of an ultrasonically actuated end effector contacts the fluid, a fine mist in the form of a diverging plume of fluid particles may emanate from the distal end of the end effector. This plume of mist is generally undesirable because it may impair the visibility of the surgical site. It would be desirable to provide an ultrasonic instrument with a reduced mist plume emanating from the distal end of the end effector when it is activated with energy at ultrasonic frequencies.